/*
Copyright 2006 Jerry Huxtable

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package com.jhlabs.math;

// TODO: Auto-generated Javadoc
/**
 * The Class FBM.
 */
public class FBM implements Function2D {

	/** The exponents. */
	protected float[] exponents;
	
	/** The H. */
	protected float H;
	
	/** The lacunarity. */
	protected float lacunarity;
	
	/** The octaves. */
	protected float octaves;
	
	/** The basis. */
	protected Function2D basis;

	/**
	 * Instantiates a new fBM.
	 * 
	 * @param H
	 *            the h
	 * @param lacunarity
	 *            the lacunarity
	 * @param octaves
	 *            the octaves
	 */
	public FBM(float H, float lacunarity, float octaves) {
		this(H, lacunarity, octaves, new Noise());
	}
	
	/**
	 * Instantiates a new fBM.
	 * 
	 * @param H
	 *            the h
	 * @param lacunarity
	 *            the lacunarity
	 * @param octaves
	 *            the octaves
	 * @param basis
	 *            the basis
	 */
	public FBM(float H, float lacunarity, float octaves, Function2D basis) {
		this.H = H;
		this.lacunarity = lacunarity;
		this.octaves = octaves;
		this.basis = basis;

		exponents = new float[(int)octaves+1];
		float frequency = 1.0f;
		for (int i = 0; i <= (int)octaves; i++) {
			exponents[i] = (float)Math.pow(frequency, -H);
			frequency *= lacunarity;
		}
	}

	/**
	 * Sets the basis.
	 * 
	 * @param basis
	 *            the new basis
	 */
	public void setBasis(Function2D basis) {
		this.basis = basis;
	}

	/**
	 * Gets the basis type.
	 * 
	 * @return the basis type
	 */
	public Function2D getBasisType() {
		return basis;
	}

	/* (non-Javadoc)
	 * @see com.jhlabs.math.Function2D#evaluate(float, float)
	 */
	public float evaluate(float x, float y) {
		float value = 0.0f;
		float remainder;
		int i;
		
		// to prevent "cascading" effects
		x += 371;
		y += 529;
		
		for (i = 0; i < (int)octaves; i++) {
			value += basis.evaluate(x, y) * exponents[i];
			x *= lacunarity;
			y *= lacunarity;
		}

		remainder = octaves - (int)octaves;
		if (remainder != 0)
			value += remainder * basis.evaluate(x, y) * exponents[i];

		return value;
	}

}
